Re: [Qemu-devel] [Qemu-ppc] [PATCH RFC 04/10] virtio-pmem: Prototype

[Murilo Opsfelder Araujo <muriloo@linux.ibm.com>]

Hi, David.

On Wed, Jan 16, 2019 at 12:35:17PM +0100, David Hildenbrand wrote:
> From: Pankaj Gupta <pagupta@redhat.com>
>
> This is the current protoype of virtio-pmem. Support will require
> machine changes for the architectures that will support it, so it will
> not yet be compiled.
>
> TODO:
> - Use separate struct for tracking requests internally
> - Move request/response structs to linux headers
> - Factor out linux header sync
> - Drop debug printfs
>
> Signed-off-by: Pankaj Gupta <pagupta@redhat.com>
> [ MemoryDevice/MemoryRegion changes, cleanups, addr property "memaddr",
>   split up patches, unplug handler ]
> Signed-off-by: David Hildenbrand <david@redhat.com>
> ---
>  hw/virtio/Makefile.objs                     |   2 +
>  hw/virtio/virtio-pmem.c                     | 189 ++++++++++++++++++++
>  include/hw/virtio/virtio-pmem.h             |  54 ++++++
>  include/standard-headers/linux/virtio_ids.h |   1 +
>  qapi/misc.json                              |  26 ++-
>  5 files changed, 271 insertions(+), 1 deletion(-)
>  create mode 100644 hw/virtio/virtio-pmem.c
>  create mode 100644 include/hw/virtio/virtio-pmem.h
>
> diff --git a/hw/virtio/Makefile.objs b/hw/virtio/Makefile.objs
> index 1b2799cfd8..5463c682f7 100644
> --- a/hw/virtio/Makefile.objs
> +++ b/hw/virtio/Makefile.objs
> @@ -9,6 +9,8 @@ obj-$(CONFIG_VIRTIO_BALLOON) += virtio-balloon.o
>  obj-$(CONFIG_VIRTIO_CRYPTO) += virtio-crypto.o
>  obj-$(call land,$(CONFIG_VIRTIO_CRYPTO),$(CONFIG_VIRTIO_PCI)) += virtio-crypto-pci.o
>
> +obj-$(CONFIG_VIRTIO_PMEM) += virtio-pmem.o
> +
>  obj-$(CONFIG_LINUX) += vhost.o vhost-backend.o vhost-user.o
>  obj-$(CONFIG_VHOST_VSOCK) += vhost-vsock.o
>  endif
> diff --git a/hw/virtio/virtio-pmem.c b/hw/virtio/virtio-pmem.c
> new file mode 100644
> index 0000000000..6fb78acf87
> --- /dev/null
> +++ b/hw/virtio/virtio-pmem.c
> @@ -0,0 +1,189 @@
> +/*
> + * Virtio PMEM device
> + *
> + * Copyright (C) 2018 Red Hat, Inc.
> + *
> + * Authors:
> + *  Pankaj Gupta <pagupta@redhat.com>
> + *  David Hildenbrand <david@redhat.com>
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2.
> + * See the COPYING file in the top-level directory.
> + */
> +
> +#include "qemu/osdep.h"
> +#include "qapi/error.h"
> +#include "qemu-common.h"
> +#include "qemu/error-report.h"
> +#include "hw/virtio/virtio-pmem.h"
> +#include "hw/virtio/virtio-access.h"
> +#include "standard-headers/linux/virtio_ids.h"
> +#include "block/aio.h"
> +#include "block/thread-pool.h"
> +
> +typedef struct VirtIOPMEMresp {
> +    int ret;
> +} VirtIOPMEMResp;
> +
> +typedef struct VirtIODeviceRequest {
> +    VirtQueueElement elem;
> +    int fd;
> +    VirtIOPMEM *pmem;
> +    VirtIOPMEMResp resp;
> +} VirtIODeviceRequest;
> +
> +static int worker_cb(void *opaque)
> +{
> +    VirtIODeviceRequest *req = opaque;
> +    int err = 0;
> +
> +    printf("\n performing flush ...");
> +    /* flush raw backing image */
> +    err = fsync(req->fd);
> +    printf("\n performed flush ...:errcode::%d", err);
> +    if (err != 0) {
> +        err = EIO;
> +    }
> +    req->resp.ret = err;
> +
> +    return 0;
> +}
> +
> +static void done_cb(void *opaque, int ret)
> +{
> +    VirtIODeviceRequest *req = opaque;
> +    int len = iov_from_buf(req->elem.in_sg, req->elem.in_num, 0,
> +                              &req->resp, sizeof(VirtIOPMEMResp));
> +
> +    /* Callbacks are serialized, so no need to use atomic ops. */
> +    virtqueue_push(req->pmem->rq_vq, &req->elem, len);
> +    virtio_notify((VirtIODevice *)req->pmem, req->pmem->rq_vq);
> +    g_free(req);
> +}
> +
> +static void virtio_pmem_flush(VirtIODevice *vdev, VirtQueue *vq)
> +{
> +    VirtIODeviceRequest *req;
> +    VirtIOPMEM *pmem = VIRTIO_PMEM(vdev);
> +    HostMemoryBackend *backend = MEMORY_BACKEND(pmem->memdev);
> +    ThreadPool *pool = aio_get_thread_pool(qemu_get_aio_context());
> +
> +    req = virtqueue_pop(vq, sizeof(VirtIODeviceRequest));
> +    if (!req) {
> +        virtio_error(vdev, "virtio-pmem missing request data");
> +        return;
> +    }
> +
> +    if (req->elem.out_num < 1 || req->elem.in_num < 1) {
> +        virtio_error(vdev, "virtio-pmem request not proper");
> +        g_free(req);
> +        return;
> +    }
> +    req->fd = memory_region_get_fd(&backend->mr);
> +    req->pmem = pmem;
> +    thread_pool_submit_aio(pool, worker_cb, req, done_cb, req);
> +}
> +
> +static void virtio_pmem_get_config(VirtIODevice *vdev, uint8_t *config)
> +{
> +    VirtIOPMEM *pmem = VIRTIO_PMEM(vdev);
> +    struct virtio_pmem_config *pmemcfg = (struct virtio_pmem_config *) config;
> +
> +    virtio_stq_p(vdev, &pmemcfg->start, pmem->start);
> +    virtio_stq_p(vdev, &pmemcfg->size, memory_region_size(&pmem->memdev->mr));
> +}
> +
> +static uint64_t virtio_pmem_get_features(VirtIODevice *vdev, uint64_t features,
> +                                        Error **errp)
> +{
> +    return features;
> +}
> +
> +static void virtio_pmem_realize(DeviceState *dev, Error **errp)
> +{
> +    VirtIODevice *vdev = VIRTIO_DEVICE(dev);
> +    VirtIOPMEM *pmem = VIRTIO_PMEM(dev);
> +
> +    if (!pmem->memdev) {
> +        error_setg(errp, "virtio-pmem memdev not set");
> +        return;
> +    } else if (host_memory_backend_is_mapped(pmem->memdev)) {
> +        char *path = object_get_canonical_path_component(OBJECT(pmem->memdev));
> +        error_setg(errp, "can't use already busy memdev: %s", path);
> +        g_free(path);
> +        return;
> +    }

Perhaps splitting this if-else block could improve readability:

    if (!pmem->memdev) {
        error_setg(...);
	return;
    }

    if (host_memory_backend_is_mapped(pmem->memdev)) {
       /* do stuff */
       return;
    }

    /* do other stuffs */

> +
> +    host_memory_backend_set_mapped(pmem->memdev, true);
> +    virtio_init(vdev, TYPE_VIRTIO_PMEM, VIRTIO_ID_PMEM,
> +                                          sizeof(struct virtio_pmem_config));

I'm not quite sure what's the QEMU style for indenting this.  There
are, for example, calls to warn_report() in other source files that
are indented at the left side after the opening parenthesis.

Perhaps indenting it like this is preferable?

    virtio_init(vdev, TYPE_VIRTIO_PMEM, VIRTIO_ID_PMEM,
                sizeof(struct virtio_pmem_config));

> +    pmem->rq_vq = virtio_add_queue(vdev, 128, virtio_pmem_flush);
> +}
> +
> +static void virtio_pmem_unrealize(DeviceState *dev, Error **errp)
> +{
> +    VirtIODevice *vdev = VIRTIO_DEVICE(dev);
> +    VirtIOPMEM *pmem = VIRTIO_PMEM(dev);
> +
> +    host_memory_backend_set_mapped(pmem->memdev, false);
> +    pmem->rq_vq = virtio_add_queue(vdev, 128, virtio_pmem_flush);
> +    virtio_cleanup(vdev);
> +}
> +
> +static void virtio_pmem_fill_device_info(const VirtIOPMEM *pmem,
> +                                         VirtioPMEMDeviceInfo *vi)
> +{
> +    vi->memaddr = pmem->start;
> +    vi->size = pmem->memdev ? memory_region_size(&pmem->memdev->mr) : 0;
> +    vi->memdev = object_get_canonical_path(OBJECT(pmem->memdev));
> +}
> +
> +static MemoryRegion *virtio_pmem_get_memory_region(VirtIOPMEM *pmem,
> +                                                   Error **errp)
> +{
> +    if (!pmem->memdev) {
> +        error_setg(errp, "'%s' property must be set", VIRTIO_PMEM_MEMDEV_PROP);
> +        return NULL;
> +    }
> +
> +    return &pmem->memdev->mr;
> +}
> +
> +static Property virtio_pmem_properties[] = {
> +    DEFINE_PROP_UINT64(VIRTIO_PMEM_ADDR_PROP, VirtIOPMEM, start, 0),
> +    DEFINE_PROP_LINK(VIRTIO_PMEM_MEMDEV_PROP, VirtIOPMEM, memdev,
> +                     TYPE_MEMORY_BACKEND, HostMemoryBackend *),
> +    DEFINE_PROP_END_OF_LIST(),
> +};
> +
> +static void virtio_pmem_class_init(ObjectClass *klass, void *data)
> +{
> +    DeviceClass *dc = DEVICE_CLASS(klass);
> +    VirtioDeviceClass *vdc = VIRTIO_DEVICE_CLASS(klass);
> +    VirtIOPMEMClass *vpc = VIRTIO_PMEM_CLASS(klass);
> +
> +    dc->props = virtio_pmem_properties;
> +
> +    vdc->realize = virtio_pmem_realize;
> +    vdc->unrealize = virtio_pmem_unrealize;
> +    vdc->get_config = virtio_pmem_get_config;
> +    vdc->get_features = virtio_pmem_get_features;
> +
> +    vpc->fill_device_info = virtio_pmem_fill_device_info;
> +    vpc->get_memory_region = virtio_pmem_get_memory_region;
> +}
> +
> +static TypeInfo virtio_pmem_info = {
> +    .name          = TYPE_VIRTIO_PMEM,
> +    .parent        = TYPE_VIRTIO_DEVICE,
> +    .class_size    = sizeof(VirtIOPMEMClass),
> +    .class_init    = virtio_pmem_class_init,
> +    .instance_size = sizeof(VirtIOPMEM),
> +};
> +
> +static void virtio_register_types(void)
> +{
> +    type_register_static(&virtio_pmem_info);
> +}
> +
> +type_init(virtio_register_types)
> diff --git a/include/hw/virtio/virtio-pmem.h b/include/hw/virtio/virtio-pmem.h
> new file mode 100644
> index 0000000000..85cee3ef39
> --- /dev/null
> +++ b/include/hw/virtio/virtio-pmem.h
> @@ -0,0 +1,54 @@
> +/*
> + * Virtio pmem device

What if "pmem" was in upper case to match the header in virtio-pmem.c?

> + *
> + * Copyright Red Hat, Inc. 2018

This is slightly different from what is in virtio-pmem.c header.
Perhaps "(C)" is missing here.

> + *
> + * Authors:
> + *  Pankaj Gupta <pagupta@redhat.com>
> + *  David Hildenbrand <david@redhat.com>
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2.
> + * See the COPYING file in the top-level directory.
> + */
> +
> +#ifndef HW_VIRTIO_PMEM_H
> +#define HW_VIRTIO_PMEM_H
> +
> +#include "hw/virtio/virtio.h"
> +#include "sysemu/hostmem.h"
> +
> +#define TYPE_VIRTIO_PMEM "virtio-pmem"
> +
> +#define VIRTIO_PMEM(obj) \
> +        OBJECT_CHECK(VirtIOPMEM, (obj), TYPE_VIRTIO_PMEM)

This indentation is slightly different from the other two macros
below.

> +#define VIRTIO_PMEM_CLASS(oc) \
> +    OBJECT_CLASS_CHECK(VirtIOPMEMClass, (oc), TYPE_VIRTIO_PMEM)
> +#define VIRTIO_PMEM_GET_CLASS(obj) \
> +    OBJECT_GET_CLASS(VirtIOPMEMClass, (obj), TYPE_VIRTIO_PMEM)
> +
> +#define VIRTIO_PMEM_ADDR_PROP "memaddr"
> +#define VIRTIO_PMEM_MEMDEV_PROP "memdev"
> +
> +typedef struct VirtIOPMEM {
> +    VirtIODevice parent_obj;
> +
> +    VirtQueue *rq_vq;
> +    uint64_t start;
> +    HostMemoryBackend *memdev;
> +} VirtIOPMEM;
> +
> +typedef struct VirtIOPMEMClass {
> +    /* private */
> +    VirtIODevice parent;
> +
> +    /* public */
> +    void (*fill_device_info)(const VirtIOPMEM *pmem, VirtioPMEMDeviceInfo *vi);
> +    MemoryRegion *(*get_memory_region)(VirtIOPMEM *pmem, Error **errp);
> +} VirtIOPMEMClass;
> +
> +struct virtio_pmem_config {
> +    uint64_t start;
> +    uint64_t size;
> +};
> +
> +#endif
> diff --git a/include/standard-headers/linux/virtio_ids.h b/include/standard-headers/linux/virtio_ids.h
> index 6d5c3b2d4f..346389565a 100644
> --- a/include/standard-headers/linux/virtio_ids.h
> +++ b/include/standard-headers/linux/virtio_ids.h
> @@ -43,5 +43,6 @@
>  #define VIRTIO_ID_INPUT        18 /* virtio input */
>  #define VIRTIO_ID_VSOCK        19 /* virtio vsock transport */
>  #define VIRTIO_ID_CRYPTO       20 /* virtio crypto */
> +#define VIRTIO_ID_PMEM         25 /* virtio pmem */
>
>  #endif /* _LINUX_VIRTIO_IDS_H */
> diff --git a/qapi/misc.json b/qapi/misc.json
> index 24d20a880a..8ae709636d 100644
> --- a/qapi/misc.json
> +++ b/qapi/misc.json
> @@ -2949,6 +2949,29 @@
>            }
>  }
>
> +##
> +# @VirtioPMEMDeviceInfo:
> +#
> +# VirtioPMEM state information
> +#
> +# @id: device's ID
> +#
> +# @memaddr: physical address in memory, where device is mapped
> +#
> +# @size: size of memory that the device provides
> +#
> +# @memdev: memory backend linked with device
> +#
> +# Since: 3.1
> +##
> +{ 'struct': 'VirtioPMEMDeviceInfo',
> +  'data': { '*id': 'str',
> +            'memaddr': 'size',
> +            'size': 'size',
> +            'memdev': 'str'
> +          }
> +}
> +
>  ##
>  # @MemoryDeviceInfo:
>  #
> @@ -2958,7 +2981,8 @@
>  ##
>  { 'union': 'MemoryDeviceInfo',
>    'data': { 'dimm': 'PCDIMMDeviceInfo',
> -            'nvdimm': 'PCDIMMDeviceInfo'
> +            'nvdimm': 'PCDIMMDeviceInfo',
> +            'virtio-pmem': 'VirtioPMEMDeviceInfo'
>            }
>  }
>
> --
> 2.17.2
>
>

--
Murilo